Modern transportation of liquids generally expends a significant amount of time and money. Though some liquids, such as water, sewage, etc., are generally transported by a pipeline, other liquids are often too delicate or too dangerous to transport by pipeline and are typically transported by tanker truck. In particular, liquid fuels are expensive, hazardous, and prone to handling error and theft, and therefore transport by tanker trucks is common for motor transportation of liquid fuels to retail outlets. In particular, liquid fuels are typically transported by tanker trucks under the recommended practices specified by the American Petroleum Institute (API) and the National Fire Protection Association (NFPA). These organizations have standards that define how liquid fuels are to be loaded, unloaded and transported within the United States. These standards have typically become common practices in most regions of the world.
The API Recommended Practice 1004 defines the use of an overfill system on conventional DOT-406 and MC-306 tanker trucks. During fuel loading, the primary means to shut off the flow of fuel is typically through a metering system at a gantry controller that measures the amount of fuel being loaded. Once a specified amount has been loaded, the gantry controller typically shuts off fuel pumps. Conventional overfill systems, however, are secondary emergency shut off systems. Conventional overfill systems generally include one or more overfill sensors mounted inside the tank, and often include one overfill sensor for each compartment of the tank. Conventional overfill systems typically communicate a permissive signal to the gantry controller to indicate that the gantry controller may load the tanker truck. When an overfill sensor becomes wet, conventional overfill systems typically prohibit the permissive signal to prevent further fuel loading, often stopping the loading process midway. Thus, conventional overfill systems generally have the primary purpose to prevent a fuel spill should the metering system fail.
These conventional overfill systems are generally electronic devices coupled to electronic sensors that are designed detect an overfill condition. Conventional overfill systems often operate in harsh and varied environments, and generally experience extreme temperatures, jostling, rocking, stretching, swaying, bumps, noxious vapors, and electrical disturbances. In particular, conventional overfill systems are typically susceptible to vibration and environmental corrosion, as well as rough handling by operators. As such, conventional overfill systems are often prone to failure. For example, sensors and wires may experience wear and intermittently send signals that may erroneously indicate a fault, or overfill condition. Similarly, sensors and wires may experience wear and intermittently fail to send signals that indicate a fault, or overfill condition. These intermittent problems may prevent loading of the tanker truck. After being denied the ability to load, operators typically return to a maintenance bay to determine the cause of the problem, but these intermittent problems are often hard to reproduce. Thus, these problems are often either ignored (possibly leading to dangerous overfills, spills, improper loading, and/or improper unloading) or addressed through potentially unnecessary and costly repair or replacement (including repair or replacement of the sensors, wires, and/or monitoring system, or even replacement of a compartment or the entire tank). As such, conventional overfill systems are typically unable to quickly and easily allow technicians to diagnose problems that occur intermittently as they are often unable to track those problems and/or reproduce those problems in a timely and efficient manner.
Furthermore, operator error is often another source of loading problems. Operators may commit a number of errors resulting in overfill and/or loading rejections from the gantry controller. Moreover, operators often commit a number of errors that result in potentially hazardous conditions, including attempting to enter an amount of fluid in excess of a compartment's capacity, connecting a filling line to an inlet for the wrong compartment than intended, and/or attempting to load a compartment that has remaining fluid from a previous load. Other typical operator errors include failing to connect the tanker truck to ground before filling, failing to establish a vapor connection between the compartment being filled and the supply tank supplying the liquid to the compartment, failing to set brakes of the tanker truck, and/or failing to engage one or more safety interlocks of the tanker truck. Conventional overfill systems are typically unable to monitor these conditions and prevent loading problems that typically occur due to operator error.
Additionally, tanker trucks are often prone to theft. As the cost of fuel rises, theft of fuel from tanker trucks generally increases. To steal the fuel, operators typically drain the bottom piping of the tanker truck that leads from the inlet to a compartment. However, this theft is often difficult to detect, as the operators typically make an unauthorized stop at some remote location and drain the fuel from the piping for personal use or black market sale. Up to about forty gallons may be drained from the bottom piping without affecting the liquid level of the compartments of the tanker truck. Conventional overfill systems are also typically unable to monitor either the tanker truck piping or the tanker truck location to detect theft of the fuel.
Moreover, errors often occur when unloading the tanker truck. One error common includes delivering a load to the wrong location, which results in non-payment by the intended recipient as well as non-payment by the unintended recipient. Another error includes unintentionally mixing fluids in tanks, which results in additional expenditures associated with pumping out that mixed fluid and proper disposal. Conventional overfill systems are unable to monitor the unloading of the tanker truck to determine errors that may occur.
Consequently, there is a continuing need to overcome these deficiencies.